U.S. patent application number 16/117766 was filed with the patent office on 2019-02-28 for gate driver and display device including the same.
This patent application is currently assigned to LG DISPLAY CO., LTD.. The applicant listed for this patent is LG DISPLAY CO., LTD.. Invention is credited to Joonki KIM, Sangjin KIM, Kyuhan YOON.
Application Number | 20190066582 16/117766 |
Document ID | / |
Family ID | 65435470 |
Filed Date | 2019-02-28 |
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United States Patent
Application |
20190066582 |
Kind Code |
A1 |
KIM; Joonki ; et
al. |
February 28, 2019 |
GATE DRIVER AND DISPLAY DEVICE INCLUDING THE SAME
Abstract
A gate driver and a display device including the same are
discussed. The gate driver includes a plurality of stages. Each
stage includes a transistor T1 configured to apply a start signal
to a node Q, a transistor Tu configured to output an emission
signal of a gate low voltage to a node Na depending on a voltage of
the node Q, a transistor T5 configured to control a voltage of a
node QB to be reversed to the voltage of the node Q, a transistor
Td configured to output the emission signal of a gate high voltage
higher than the gate low voltage to the node Na depending on the
voltage of the node QB, and a transistor Tbv connected between the
transistor T1 and the node Q and configured to stabilize the
voltage of the node Q.
Inventors: |
KIM; Joonki; (PAJU-SI,
KR) ; YOON; Kyuhan; (PAJU-SI, KR) ; KIM;
Sangjin; (PAJU-SI, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG DISPLAY CO., LTD. |
Seoul |
|
KR |
|
|
Assignee: |
LG DISPLAY CO., LTD.
SEOUL
KR
|
Family ID: |
65435470 |
Appl. No.: |
16/117766 |
Filed: |
August 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G09G 2300/0861 20130101;
G09G 3/3233 20130101; G09G 2310/0262 20130101; G09G 2310/0251
20130101; G09G 2310/0286 20130101; G09G 3/3266 20130101; G09G
2310/08 20130101; H01L 27/3276 20130101 |
International
Class: |
G09G 3/3233 20060101
G09G003/3233; G09G 3/3266 20060101 G09G003/3266; G09G 3/3291
20060101 G09G003/3291; G09G 3/3258 20060101 G09G003/3258; H01L
27/32 20060101 H01L027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2017 |
KR |
10-2017-0110221 |
Claims
1. A gate driver comprising: a plurality of stages, wherein each of
the plurality of stages includes: a transistor T1 configured to
apply a start signal to a node Q; a transistor Tu configured to
output an emission signal of a gate low voltage to a node Na
depending on a voltage of the node Q; a transistor T5 configured to
control a voltage of a node QB to be reversed to the voltage of the
node Q; a transistor Td configured to output the emission signal of
a gate high voltage higher than the gate low voltage to the node Na
depending on the voltage of the node QB; and a transistor Tbv
connected between the transistor T1 and the node Q and configured
to stabilize the voltage of the node Q.
2. The gate driver of claim 1, further comprising a capacitor C1
provided between a gate electrode of the transistor Tbv and the
node Q and configured to stabilize the voltage of the node Q,
wherein the gate low voltage is applied to the gate electrode of
the transistor Tbv.
3. The gate driver of claim 1, further comprising: a transistor T2
configured to apply a clock signal ECLK2 to a node Q' in response
to the start signal; a transistor T3 configured to apply the gate
low voltage to the node Q' in response to the clock signal ECLK2; a
capacitor CQ' connected between the node Q' and a node Nb and
configured to bootstrap a voltage of the node Q' to a voltage level
lower than the gate low voltage in response to a clock signal ECLK1
which is out of phase with the clock signal ECLK2; a transistor T4
configured to apply the clock signal ECLK1 to the node Nb depending
on the voltage of the node Q'; and a transistor T5 including a gate
electrode and a first electrode that are connected to the node Nb,
and a second electrode connected to the node QB.
4. The gate driver of claim 3, wherein a gate electrode of the
transistor T2 is directly connected to an input terminal of the
start signal.
5. The gate driver of claim 4, wherein for a certain period of time
from a time at which the emission signal is inverted from the gate
high voltage to the gate low voltage, the voltage of the node Q is
held at the gate low voltage capable of turning on the transistor
Tu, the voltage of the node QB is held at the gate high voltage
capable of turning off the transistor Td, and the voltage of the
node Q' swings between the gate low voltage and the gate high
voltage in synchronization with the clock signal ECLK2.
6. The gate driver of claim 1, wherein a gate electrode of the
transistor Tu is connected to the node Q, a first electrode of the
transistor Tu is connected to the node Na, and a second electrode
of the transistor Tu is connected to an input terminal of the gate
low voltage, wherein a gate electrode of the transistor Td is
connected to the node QB, a first electrode of the transistor Td is
connected to an input terminal of the gate high voltage, and a
second electrode of the transistor Td is connected to the node
Na.
7. The gate driver of claim 6, further comprising a capacitor CQ
connected between the node Q and the node Na.
8. The gate driver of claim 6, further comprising a capacitor CQB
connected between the node QB and the input terminal of the gate
high voltage.
9. A gate driver comprising: a plurality of stages, wherein each of
the plurality of stages includes: a transistor Tu connected between
an input terminal of a gate low voltage and a node Na and
configured to output an emission signal of the gate low voltage
depending on a voltage of a node Q; a transistor Td connected
between an input terminal of a gate high voltage and the node Na
and configured to output the emission signal of the gate high
voltage depending on a voltage of a node QB; and a node controller
configured to control the voltage of the node Q, the voltage of the
node QB, and a voltage of a node Q' between the input terminal of
the gate low voltage and the node QB based on a start signal of
which a phase is earlier than a phase of the emission signal, and a
first clock signal and a second clock signal that are in antiphase,
wherein for a certain period of time from a time at which the
emission signal is inverted from the gate high voltage to the gate
low voltage, the voltage of the node Q is held at the gate low
voltage capable of turning on the transistor Tu.
10. The gate driver of claim 9, wherein for the certain period of
time, the voltage of the node QB is held at the gate high voltage
capable of turning off the transistor Td, and the voltage of the
node Q' swings between the gate low voltage and the gate high
voltage in synchronization with the second clock signal.
11. The gate driver of claim 9, wherein the node controller
includes: a transistor T1 configured to apply the start signal to
the node Q; a transistor T5 configured to control the voltage of
the node QB to be reversed to the voltage of the node Q; and a
transistor Tbv connected between the transistor T1 and the node Q
and configured to stabilize the voltage of the node Q to the gate
low voltage for the certain period of time.
12. The gate driver of claim 11, further comprising a capacitor C1
provided between a gate electrode of the transistor Tbv and the
node Q and configured to stabilize the voltage of the node Q,
wherein the gate low voltage is applied to the gate electrode of
the transistor Tbv.
13. The gate driver of claim 9, wherein the node controller
includes: a transistor T2 configured to apply the second clock
signal to the node Q' in response to the start signal; a transistor
T3 configured to apply the gate low voltage to the node Q' in
response to the second clock signal; a capacitor CQ' connected
between the node Q' and a node Nb and configured to bootstrap the
voltage of the node Q' to a voltage level lower than the gate low
voltage in response to the first clock signal; a transistor T4
configured to apply the first clock signal to the node Nb depending
on the voltage of the node Q'; and a transistor T5 including a gate
electrode and a first electrode that are connected to the node Nb,
and a second electrode connected to the node QB.
14. The gate driver of claim 13, wherein a gate electrode of the
transistor T2 is directly connected to an input terminal of the
start signal.
15. The gate driver of claim 9, wherein the node controller
includes a capacitor CQ connected between the node Q and the node
Na.
16. The gate driver of claim 9, wherein the node controller
includes a capacitor CQB connected between the node QB and the
input terminal of the gate high voltage.
17. A display device comprising: a display panel including a
plurality of gate lines connected to a plurality of pixels; and the
gate driver configured to drive the gate lines using outputs of the
stages according to claim 1.
18. The display device of claim 17, wherein each of the plurality
of pixels includes: an organic light emitting diode; a driving thin
film transistor configured to control a driving current flowing in
the organic light emitting diode depending on a gate-to-source
voltage; and an emission thin film transistor turned on or off in
response to an emission signal and configured to determine an
emission time of the organic light emitting diode.
19. A display device comprising: a display panel including a
plurality of gate lines connected to a plurality of pixels; and the
gate driver configured to drive the gate lines using outputs of the
stages according to claim 9.
20. The display device of claim 19, wherein each of the plurality
of pixels includes: an organic light emitting diode; a driving thin
film transistor configured to control a driving current flowing in
the organic light emitting diode depending on a gate-to-source
voltage; and an emission thin film transistor turned on or off in
response to an emission signal and configured to determine an
emission time of the organic light emitting diode.
Description
[0001] This application claims the priority benefit of Korea Patent
Application No. 10-2017-0110221 filed on Aug. 30, 2017 in the
Republic of Korea, which is incorporated herein by reference for
all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present disclosure relates to a gate driver and a
display device including the same.
Discussion of the Related Art
[0003] An electroluminescent display is classified into an
inorganic electroluminescent display and an organic
electroluminescent display depending on a material of an emission
layer. An active matrix organic light emitting diode (OLED) display
includes a plurality of OLEDs capable of emitting light by
themselves and has many advantages of fast response time, high
emission efficiency, high luminance, wide viewing angle, and the
like.
[0004] An OLED display includes pixels arranged in a matrix and
adjusts a luminance of the pixels in accordance with gray levels of
image data. Each pixel includes an OLED, a driving thin film
transistor (TFT) controlling a driving current flowing in the OLED
depending on a gate-to-source voltage of the driving TFT, and
switching TFTs programming the gate-to-source voltage of the
driving TFT in response to a scan signal. The pixel adjusts a
display gray level (or a luminance) with an amount of light emitted
by the OLED proportional to the driving current. Each pixel may
further include an emission TFT that is turned on or off in
response to an emission signal and determines an emission time of
the OLED.
[0005] The OLED display includes a scan driver for generating the
scan signal and an emission driver for generating the emission
signal. The scan driver and the emission driver constitute a gate
driver.
[0006] The scan driver sequentially supplies the scan signals to
first gate lines. Gate electrodes of the switching TFTs are
connected to the scan driver through the first gate lines. The
emission driver sequentially supplies the emission signals to
second gate lines. Gate electrodes of the emission TFTs are
connected to the emission driver through the second gate lines.
[0007] The emission driver may be implemented as a gate shift
register including a plurality of stages. Each stage outputs the
emission signal at a gate high voltage or a gate low voltage
depending on a voltage of a node Q and a voltage of a node QB. The
emission signal of the gate high voltage is a signal capable of
turning off the emission TFTs, and the emission signal of the gate
low voltage is a signal capable of turning on the emission TFTs.
The emission signal of the gate high voltage is output while the
node Q is deactivated, and the emission signal of the gate low
voltage is output while the node Q is activated.
[0008] When the emission signal of the gate low voltage is output,
an initialization operation and an emission operation of the pixels
are performed. To secure operation stability of the pixels, the
node Q has to maintain an activation state in an initialization
period and an emission period. The voltage of the node Q is
affected by change in the characteristics of internal elements
connected to the node Q. When the electrical characteristics of the
internal elements connected to the node Q change due to various
factors including a temperature, a bias voltage, deterioration,
etc., the voltage of the node Q may swing. Further, the emission
signal is not held at the gate low voltage and may increase to a
voltage higher than the gate low voltage. In this instance, the
reliability of the display device can be greatly reduced.
SUMMARY OF THE INVENTION
[0009] Accordingly, an object of the present disclosure is to
address the above-described and other problems and provide a gate
driver capable of securing operation stability of an emission
driver and improving reliability of the emission driver and a
display device including the gate driver.
[0010] In one aspect, there is provided a gate driver comprising a
plurality of stages, wherein each stage includes a transistor T1
configured to apply a start signal to a node Q, a transistor Tu
configured to output an emission signal of a gate low voltage to a
node Na depending on a voltage of the node Q, a transistor T5
configured to control a voltage of a node QB to be reversed to the
voltage of the node Q, a transistor Td configured to output the
emission signal of a gate high voltage higher than the gate low
voltage to the node Na depending on the voltage of the node QB, and
a transistor Tbv connected between the transistor T1 and the node Q
and configured to stabilize the voltage of the node Q.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, that may be included to provide a
further understanding of the disclosure and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the disclosure and together with the description serve to explain
various principles of the disclosure.
[0012] FIG. 1 illustrates a display device according to an
embodiment of the disclosure.
[0013] FIG. 2 illustrates a pixel array included in a display panel
shown in FIG. 1.
[0014] FIG. 3 schematically illustrates a pixel circuit included in
a pixel array shown in FIG. 2.
[0015] FIG. 4 illustrates a gate signal applied to the pixel
circuit shown in FIG. 3.
[0016] FIG. 5 illustrates a scan driver and an emission driver
included in a gate driver shown in FIG. 1.
[0017] FIG. 6 illustrates configuration of a gate shift register
included in an emission driver shown in FIG. 5.
[0018] FIG. 7 illustrates configuration of a stage included in the
gate shift register shown in FIG. 6.
[0019] FIG. 8 illustrates an operation waveform of a stage shown in
FIG. 7.
[0020] FIGS. 9A to 9G illustrate operation states of a stage
respectively corresponding to periods {circle around (1)} to
{circle around (7)} shown in FIG. 8.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] Reference will now be made in detail to embodiments of the
disclosure, examples of which are illustrated in the accompanying
drawings. However, the present disclosure is not limited to
embodiments disclosed below, and may be implemented in various
forms. These embodiments are provided so that the present
disclosure will be described more completely, and will fully convey
the scope of the present disclosure to those skilled in the art to
which the present disclosure pertains. Particular features of the
present disclosure can be defined by the scope of the claims.
[0022] Shapes, sizes, ratios, angles, number, and the like
illustrated in the drawings for describing embodiments of the
disclosure are merely exemplary, and the present disclosure is not
limited thereto unless specified as such. Like reference numerals
designate like elements throughout. In the following description,
when a detailed description of certain functions or configurations
related to this document that may unnecessarily cloud the gist of
the invention have been omitted.
[0023] In the present disclosure, when the terms "include", "have",
"comprised of", etc. are used, other components may be added unless
".about. only" is used. A singular expression can include a plural
expression as long as it does not have an apparently different
meaning in context.
[0024] In the explanation of components, even if there is no
separate description, it is interpreted as including margins of
error or an error range.
[0025] In the description of positional relationships, when a
structure is described as being positioned "on or above", "under or
below", "next to" another structure, this description should be
construed as including a case in which the structures directly
contact each other as well as a case in which a third structure is
disposed therebetween.
[0026] The terms "first", "second", etc. may be used to describe
various components, but the components are not limited by such
terms. The terms are used only for the purpose of distinguishing
one component from other components. For example, a first component
may be designated as a second component, and vice versa, without
departing from the scope of the present disclosure.
[0027] In embodiments disclosed herein, each of a pixel circuit and
a gate driver on a substrate of a display panel can be implemented
as transistors of p-type metal oxide semiconductor field effect
transistor (MOSFET) structure. However, embodiments are not limited
thereto. The transistor is a three-electrode element including a
gate, a source, and a drain. The source is an electrode for
supplying carriers to the transistor. The carriers inside the
transistor begin to flow from the source. The drain is an electrode
from which the carriers exit the transistor. Namely, carriers in
the MOSFET flow from the source to the drain. In case of a p-type
thin film transistor (TFT) (or p-type MOSFET (PMOS)), because
carriers are holes, a source voltage is greater than a drain
voltage so that holes can flow from a source to a drain. In the
p-type TFT, because holes flow from the source to the drain, a
current flows from the source to the drain. It should be noted that
the source and the drain of the MOSFET are not fixed. For example,
the source and the drain of the MOSFET may be changed depending on
an applied voltage. Thus, in embodiments disclosed herein, one of
the source and the drain is referred to as a first electrode, and
the other is referred to as a second electrode.
[0028] The following embodiments are described using an organic
light emitting diode (OLED) display including an organic light
emitting material as an example of a display device. However, it
should be noted that the technical idea of the present disclosure
is not limited to the OLED display. For example, the present
disclosure may be applied to an inorganic electroluminescent
display including an inorganic electroluminescent material. All the
components of the displays and display devices according to all
embodiments of the present disclosure are operatively coupled and
configured.
[0029] FIG. 1 illustrates a display device according to an
embodiment of the disclosure. FIG. 2 illustrates a pixel array
included in a display panel shown in FIG. 1. FIG. 3 schematically
illustrates a pixel circuit included in a pixel array shown in FIG.
2. FIG. 4 illustrates a gate signal applied to the pixel circuit
shown in FIG. 3. FIG. 5 illustrates a scan driver and an emission
driver included in a gate driver shown in FIG. 1.
[0030] Referring to FIG. 1, the display device according to an
embodiment of the disclosure includes a display panel 100, one or
more timing controllers 110, one or more data drivers 120, one or
more gate drivers 130, and one or more level shifters 150, and the
like.
[0031] A plurality of data lines 14 and a plurality of gate lines
15a and 15b are disposed to intersect each other on the display
panel 100. Pixels PXL are respectively arranged at intersections of
the data lines 14 and the gate lines 15a and 15b in a matrix to
form a pixel array.
[0032] As shown in FIG. 2, the pixel array of the display panel 100
includes a plurality of horizontal pixel lines L1 to L4. The pixels
PXL, which are horizontally adjacent to one another and are
commonly connected to the gate lines 15a and 15b, are disposed on
each of the horizontal pixel lines L1 to L4. In embodiments
disclosed herein, each of the horizontal pixel lines L1 to L4 is
not a physical signal line but a block of pixels implemented by
horizontally adjacent pixels PXL of one line. The pixel array can
include first power lines 17 supplying a high potential power
voltage EVDD to the pixels PXL and second power lines 16 supplying
a reference voltage Vref to the pixels PXL. Further, the pixels PXL
can be connected to an input terminal of a low potential power
voltage EVSS.
[0033] As shown in FIG. 2, each gate line can include a first gate
line 15a supplied with a scan signal SCAN and a second gate line
15b supplied with an emission signal EM.
[0034] Each pixel PXL can be one of a red pixel, a green pixel, a
blue pixel, and a white pixel for implementation of various colors.
A red pixel, a green pixel, a blue pixel, and a white pixel can
constitute a unit pixel. A color implemented by the unit pixel can
be determined depending on an emission rate of the red pixel, the
green pixel, the blue pixel, and the white pixel. Each pixel PXL
can be connected to the data line 14, the first gate line 15a, the
second gate line 15b, the first power line 17, the second power
line 16, and the like.
[0035] As shown in FIG. 3, each pixel PXL can include an organic
light emitting diode (OLED), a driving thin film transistor (TFT)
DT controlling a driving current flowing in the OLED depending on a
gate-to-source voltage of the driving TFT DT, a switch circuit SWC
for programming the gate-to-source voltage of the driving TFT DT,
and an emission TFT ET that is turned on or off in response to the
emission signal EM and determines an emission time of the OLED. The
switch circuit SWC can include a plurality of switching TFTs, one
or more capacitors, and the like. The switch circuit SWC can be
variously modified depending on model and specification of the
product. The TFTs included in each pixel PXL can be implemented as
PMOS low-temperature polycrystalline silicon (LTPS) TFTs, and thus
each pixel PXL can secure desired response characteristics through
the PMOS LTPS TFTs. However, embodiments are not limited thereto.
For example, at least one of the TFTs can be implemented as an NMOS
oxide TFT having good off-current characteristics, and other TFTs
can be implemented as PMOS LTPS TFTs having good response
characteristics.
[0036] Each pixel PXL can be driven in response to a gate signal
shown in FIG. 4. Each pixel PXL can perform an initialization
operation, a programming operation, and an emission operation in
response to a scan signal SCAN and an emission signal EM shown in
FIG. 4. In an initialization period A, the switch circuit SWC
initializes specific nodes of a pixel circuit to the reference
voltage Vref and can secure stability and reliability of the
initialization operation. In a programming period B, the switch
circuit SWC can program the gate-to-source voltage of the driving
TFT DT based on a data voltage Vdata, and a threshold voltage of
the driving TFT DT can be compensated. In an emission period C, a
driving current corresponding to the gate-to-source voltage flows
between a source and a drain of the driving TFT DT, and the OLED
emits light with the driving current.
[0037] The emission TFT ET can be turned on in the initialization
period A and the emission period C and can be turned off in the
programming period B in response to the emission signal EM.
[0038] In FIG. 4, a gate-on voltage is a voltage of the gate signal
capable of turning on the TFT, and a gate-off voltage is a voltage
of the gate signal capable of turning off the TFT. For example, a
gate-on voltage in the PMOS is a gate low voltage VGL, and a
gate-off voltage in the PMOS is a gate high voltage VGH higher than
the gate low voltage VGL.
[0039] Referring to FIG. 1, for each data driver 120, the data
driver 120 receives image data DATA from the timing controller 110.
The data driver 120 converts the image data DATA into gamma
compensation voltages in response to a source timing control signal
DDC received from the timing controller 110 and generates data
voltages Vdata. The data driver 120 synchronizes the data voltage
Vdata with the scan signal SCAN and supplies the data voltage Vdata
to the data lines 14 of the display panel 100. The data driver 120
can be connected to the data lines 14 of the display panel 100
through a chip-on glass (COG) process or a tape automated bonding
(TAB) process.
[0040] Referring to FIG. 1, each level shifter 150 boosts a
transistor-transistor logic (TTL) level voltage of a gate timing
control signal GDC received from the timing controller 110 to the
gate high voltage VGH and the gate low voltage VGL capable of
driving the TFTs of the display panel 100 and supplies them to the
gate driver(s) 130. The gate timing control signal GDC can include
an external start signal, a clock signal, and the like.
[0041] Referring to FIG. 1, for each gate driver 130, the gate
driver 130 operates in response to the gate timing control signal
GDC received from the level shifter 150 and generates the gate
signals. The gate driver 130 sequentially supplies the gate signals
to the gate lines. The gate driver 130 can be directly formed on a
lower substrate of the display panel 100 using a gate driver-in
panel (GIP) manner. The gate driver 130 is formed in a non-display
area (i.e., a bezel area BZ) outside a screen of the display panel
100. In the GIP manner, the level shifter 150 can be mounted on a
printed circuit board (PCB) 140 together with the timing controller
110.
[0042] As shown in FIG. 5, the gate drivers 130 are disposed on
opposite sides of the display panel 100 in a double bank structure
and can reduce signal distortion resulting from a load variation.
The gate driver 130 includes a scan driver 131 generating the scan
signal SCAN and an emission driver 132 generating the emission
signal EM.
[0043] The scan driver 131 can supply the scan signals SCAN to
first gate lines 15a(1) to 15a(n) in a line sequential manner. The
emission driver 132 can supply the emission signals EM to second
gate lines 15b(1) to 15b(n) in a line sequential manner. The
emission driver 132 can be implemented as a gate shift register
including a plurality of stages. Each stage of the emission driver
132 can be implemented as shown in FIGS. 6 to 9G in order to secure
stability and reliability of an operation.
[0044] Referring to FIG. 1, the timing controller 110 can be
connected to an external host system through known various
interface manners. The timing controller 110 receives the image
data DATA from the host system. The timing controller 110 can
correct the image data DATA and then transmit the corrected image
data DATA to the data drivers 120, so that a luminance variation
resulting from a difference between electrical characteristics of
the pixels PXL is compensated.
[0045] The timing controller 110 receives timing signals such as a
vertical sync signal Vsync, a horizontal sync signal Hsync, a data
enable signal DE, and a main clock MCLK from the host system. The
timing controller 110 can generate the gate timing control signal
GDC and the source timing control signal DDC based on the timing
signals.
[0046] FIG. 6 illustrates configuration of example of a gate shift
register included in the emission driver shown in FIG. 5.
[0047] Referring to FIG. 6, the emission driver 132 according to
the embodiment of the disclosure can be implemented as a gate shift
register including a plurality of stages ST1 to ST4, . . . .
Although 5 stages are discussed, the stages can be in different
numbers. The stages ST1 to ST4, . . . can be GIP elements formed in
the GIP manner.
[0048] Operations of the stages ST1 to ST4, . . . are sequentially
activated in response to a start signal and output emission signals
EM(1) to EM(4), . . . An operation of the uppermost stage ST1 is
activated in response to an external start signal EVST, and
operations of the second uppermost stage ST2 below the uppermost
stage ST1 to a lowermost stage are activated in response to an
emission signal of a preceding stage. The emission signal of the
preceding stage is used as an internal start signal and is a carry
signal CRY. In embodiments disclosed herein, "preceding stage" is a
stage that is activated earlier than a reference stage and
generates an emission signal of which a phase is earlier than a
phase of an emission signal output from the reference stage.
[0049] The stages ST1 to ST4, . . . receive the external start
signal EVST, a first clock signal ECLK1, and a second clock signal
ECLK2 from the level shifter 150 in order to output the emission
signals EM(1) to EM(4), . . . The external start signal EVST, the
first clock signal ECLK1, and the second clock signal ECLK2 can
swing between the gate high voltage VGH and the gate low voltage
VGL.
[0050] The external start signal EVST is input to the uppermost
stage ST1, and the first clock signal ECLK1 and the second clock
signal ECLK2 are input to all the stages ST1 to ST4, . . . The
first clock signal ECLK1 and the second clock signal ECLK2 are in
antiphase. Thus, input positions of the first clock signal ECLK1
and the second clock signal ECLK2 in odd-numbered stages can be set
to be opposite to those in even-numbered stages, in order to
normally operate each of the stages that are connected in cascade.
For example, when the first clock signal ECLK1 is input to first
terminals of the odd-numbered stages and the second clock signal
ECLK2 is input to second terminals of the odd-numbered stages, the
first clock signal ECLK1 can be input to second terminals of the
even-numbered stages and the second clock signal ECLK2 can be input
to first terminals of the even-numbered stages.
[0051] Each of the stages ST1 to ST4, . . . activates an operation
of a node Q in response to the start signal applied to a start
terminal in each frame. In embodiments disclosed herein, the fact
that a node is activated indicates that the gate low voltage VGL or
a voltage corresponding to the gate low voltage VGL is applied to
the node. Further, the fact that a node is deactivated indicates
that the gate high voltage VGH or a voltage corresponding to the
gate high voltage VGH is applied to the node.
[0052] Each of the stages ST1 to ST4, . . . receives the gate high
voltage VGH and the gate low voltage VGL from an external power
supply unit. For example, the gate high voltage VGH can be set to
20V to 30V, and the gate low voltage VGL can be set to -10V to 0V.
However, embodiments are not limited thereto.
[0053] FIG. 7 illustrates configuration of the uppermost stage ST1
included in the gate shift register shown in FIG. 6.
[0054] Configurations of the remaining odd-numbered stages except
the uppermost stage ST1 are substantially the same as configuration
of the uppermost stage ST1, except that they receive the internal
start signal CRY instead of the external start signal EVST and each
output a corresponding emission signal. Further, configurations of
the even-numbered stages are substantially the same as
configuration of the uppermost stage ST1, except that they receive
the internal start signal CRY instead of the external start signal
EVST, receives the second clock signal ECLK2 instead of the first
clock signal ECLK1, receives the first clock signal ECLK1 instead
of the second clock signal ECLK2, and each output a corresponding
emission signal.
[0055] Referring to FIG. 7, the stage ST1 outputs an emission
signal EM(1) of the gate high voltage VGH while the node Q is
deactivated to the gate high voltage VGH and a node QB is activated
to the gate low voltage VGL. Further, the stage ST1 outputs the
emission signal EM(1) of the gate low voltage VGL while the node Q
is activated to the gate low voltage VGL and the node QB is
deactivated to the gate high voltage VGH.
[0056] To this end, the stage ST1 can include a transistor Tu
outputting the emission signal EM(1) of the gate low voltage VGL to
a node Na, a transistor Td outputting the emission signal EM(1) of
the gate high voltage VGH to the node Na, and a node controller NCP
controlling voltages of nodes Q, Q' and QB.
[0057] The transistor Tu is an output buffer of which an operation
is controlled depending on the voltage of the node Q. The
transistor Tu is turned off when the node Q is deactivated to the
gate high voltage VGH, and is turned on when the node Q is
activated to the gate low voltage VGL. A gate electrode of the
transistor Tu is connected to the node Q, a first electrode of the
transistor Tu is connected to the node Na, and a second electrode
of the transistor Tu is connected to an input terminal of the gate
low voltage VGL.
[0058] The transistor Td is an output buffer of which an operation
is controlled depending on the voltage of the node QB. The
transistor Td is turned off when the node QB is deactivated to the
gate high voltage VGH, and is turned on when the node QB is
activated to the gate low voltage VGL. A gate electrode of the
transistor Td is connected to the node QB, a first electrode of the
transistor Td is connected to an input terminal of the gate high
voltage VGH, and a second electrode of the transistor Td is
connected to the node Na.
[0059] The node controller NCP controls the voltage of the node Q,
the voltage of the node QB, and the voltage of the node Q' between
the input terminal of the gate low voltage VGL and the node QB
based on an external start signal EVST of which a phase is earlier
than a phase of the emission signal EM(1), the first clock signal
ECLK1 and the second clock signal ECLK2 that are in antiphase, the
gate low voltage VGL, and the gate high voltage VGH.
[0060] The node controller NCP controls the voltage of the node Q
and the voltage of the node QB to be reversed for a remaining time
excluding an initial time (e.g., a period {circle around (2)} of
FIG. 8) from one frame. For example, for the remaining time, when
the voltage of the node Q is the gate high voltage VGH, the voltage
of the node QB can be the gate low voltage VGL. On the contrary,
when the voltage of the node Q is the gate low voltage VGL, the
voltage of the node QB can be the gate high voltage VGH.
[0061] The voltage of the node Q is affected by change in
characteristics of internal elements included in the node
controller NCP. When electrical characteristics of the internal
elements change due to various factors including a temperature, a
bias voltage, deterioration, etc., the voltage of the node Q can
swing for a certain period of time (for example, including periods
{circle around (6)} and {circle around (7)} of FIG. 8). Further,
the emission signal EM(1) is not held at the gate low voltage VGL
and can increase to a voltage level higher than the gate low
voltage VGL. Even when the voltage of the node QB swings, the
emission signal EM(1) is not held at the gate high voltage VGH and
can decrease to a voltage level lower than the gate high voltage
VGH for a predetermined time (for example, including periods
{circle around (3)}, {circle around (4)} and {circle around (5)} of
FIG. 8). In this instance, the reliability of the display device
can be greatly reduced.
[0062] The node controller NCP includes a plurality of
stabilization configurations and stabilizes the voltages of the
node Q and the node QB.
[0063] The node controller NCP includes at least one of a
connection configuration of a transistor Tbv and a transistor T2
and a capacitor CQ to thereby simplify circuit configuration of the
stage and to stabilize the voltage of the node Q for the certain
period of time. Through the above stabilization configurations, the
node controller NCP can hold the voltage of the node Q at the gate
low voltage VGL capable of turning on the transistor Tu for the
certain period of time from a time at which the emission signal
EM(1) is inverted from the gate high voltage VGH to the gate low
voltage VGL. Further, for the certain period of time, the node
controller NCP can hold the voltage of the node QB at the gate high
voltage VGH capable of turning off the transistor Td and can swing
the voltage of the node Q' between the gate low voltage VGL and the
gate high voltage VGH in synchronization with the second clock
signal ECLK2. Hence, the operation stability and the operation
reliability of the stage ST1 can be secured.
[0064] The node controller NCP includes a capacitor CQB to thereby
stabilize the voltage of the node QB for the predetermined time.
Hence, the operation reliability of the stage ST1 can further
increase.
[0065] More specifically, the node controller NCP can include a
plurality of transistors T1 to T6 and Tbv and a plurality of
capacitors CQ, CQ' and CQB.
[0066] Each of the plurality of transistors T1 to T6 can be
designed in a dual gate structure, in order to suppress a leakage
current when the transistor is turned off. In the dual gate
structure, a first gate electrode and a second gate electrode of
the transistor are connected to each other so that they have the
same voltage level. A channel length of the dual gate structure is
longer than a channel length of a single gate structure. Because an
increase in the channel length results in an increase in a
resistance, the leakage current decreases when the transistor is
turned off. Hence, the operation stability can be secured.
[0067] The transistor T1, the transistor Tbv, and the capacitor CQ
are elements controlling the voltage of the node Q.
[0068] The transistor T1 applies the external start signal EVST to
the node Q in response to the second clock signal ECLK2. A gate
electrode of the transistor T1 is connected to an input terminal of
the second clock signal ECLK2. A first electrode of the transistor
T1 is connected to a start terminal to which the external start
signal EVST is input, and a second electrode of the transistor T1
is connected to one electrode of the transistor Tbv.
[0069] The transistor Tbv is connected between the transistor T1
and the node Q and stabilizes the voltage of the node Q to the gate
low voltage VGL for the certain period of time, thereby preventing
distortion of the emission signal EM(1). To this end, a capacitor
C1 is provided between a gate electrode of the transistor Tbv and
the node Q to stabilize the voltage of the node Q. The gate
electrode of the transistor Tbv is connected to the input terminal
of the gate low voltage VGL. A first electrode of the transistor
Tbv is connected to the transistor T1, and a second electrode of
the transistor Tbv is connected to the node Q.
[0070] The transistor Tbv is connected between the transistor T1
and the node Q and prevents a breakdown phenomenon, thereby
protecting the GIP elements. If the transistor T1 is directly
connected to the node Q, a source-to-drain voltage of the
transistor T1 can increase depending on change in the voltage of
the node Q, and a load applied to the transistor T1 can increase.
However, the transistor Tbv according to the embodiment of the
disclosure can reduce an influence of the node Q applied to the
transistor T1 and thus protect the transistor T1.
[0071] The capacitor CQ is connected between the node Q and the
node Na. The capacitor CQ couples the node Q to the node Na to
which the emission signal EM(1) is output, thereby stabilizing the
voltage of the node Q.
[0072] The transistor T2, the transistor T3, the transistor T4, and
the capacitor CQ' are elements controlling the voltage of the node
Q'.
[0073] The transistor T2 applies the second clock signal ECLK2 to
the node Q' in response to the external start signal EVST. A gate
electrode of the transistor T2 is connected to the start terminal
to which the external start signal EVST is input. A first electrode
of the transistor T2 is connected to the input terminal of the
second clock signal ECLK2, and a second electrode of the transistor
T2 is connected to the node Q'.
[0074] The transistor T3 applies the gate-low voltage VGL to the
node Q' in response to the second clock signal ECLK2. A gate
electrode of the transistor T3 is connected to the input terminal
of the second clock signal ECLK2. A first electrode of the
transistor T3 is connected to the input terminal of the gate low
voltage VGL, and a second electrode of the transistor T3 is
connected to the node Q'.
[0075] The transistor T4 applies the first clock signal ECLK1 to a
node Nb depending on the voltage of the node Q'. A gate electrode
of the transistor T4 is connected to the node Q'. A first electrode
of the transistor T4 is connected to an input terminal of the first
clock signal ECLK1, and a second electrode of the transistor T4 is
connected to the node Nb.
[0076] The capacitor CQ' is connected between the node Q' and the
node Nb. The capacitor CQ' bootstraps the voltage of the node Q' to
a voltage less than the gate low voltage VGL in response to the
first clock signal ECLK1.
[0077] The transistor T5, the transistor T6, and the capacitor CQB
are elements controlling the voltage of the node QB.
[0078] The transistor T5 is diode-connected between the node Nb and
the node QB. The transistor T5 is turned on when the node Q' is
bootstrapped, and thus reduces the voltage of the node QB to the
gate low voltage VGL. Because the voltage of the node Nb can be
stably and rapidly reduced to the gate low voltage VGL due to the
bootstrapping of the node Q', operation stability of the transistor
T5 is secured. A gate electrode and a first electrode of the
transistor T5 are connected to the node Nb, and a second electrode
of the transistor T5 is connected to the node QB.
[0079] The transistor T6 controls the current flowing between the
input terminal of the gate high voltage VGH and the node QB
depending on the voltage of the node Q. When the node Q is
activated to the gate low voltage VGL, the transistor T6 connects
the node QB to the input terminal of the gate high voltage VGH and
deactivates the node QB to the gate high voltage VGH.
[0080] The capacitor CQB is connected between the node QB and the
input terminal of the gate high voltage VGH. When the node QB is
coupled to the input terminal of the gate high voltage VGH, the
voltage of the node QB can be stably held even while the node QB is
floated.
[0081] FIG. 8 illustrates an operation waveform of the stage shown
in FIG. 7. FIGS. 9A to 9G illustrate operation states of a stage
respectively corresponding to periods {circle around (1)} to
{circle around (7)} shown in FIG. 8.
[0082] Referring to FIGS. 8 and 9A, in a period {circle around
(1)}, the external start signal EVST is input at the gate low
voltage VGL, and the first and second clock signals ECLK1 and ECLK2
are input at the gate high voltage VGH.
[0083] In the period {circle around (1)}, the transistor T2 is
turned on in response to the external start signal EVST of the gate
low voltage VGL, and the transistors T1 and T3 are turned off in
response to the second clock signal ECLK2 of the gate high voltage
VGH.
[0084] In the period {circle around (1)}, the node Q is floated by
the turn-off of the transistor T1. However, the voltage of the node
Q is stabilized by the capacitor C1 coupled to the gate electrode
of the transistor Tbv and the capacitor CQ coupled to the node Na.
The node Q is activated to the gate low voltage VGL. The
transistors T6 and Tu are turned on in response to the activated
node Q.
[0085] In the period {circle around (1)}, the node Q' is
deactivated to the gate high voltage VGH by the second clock signal
ECLK2 applied through the transistor T2. The transistor T4 is
turned off in response to the deactivated node Q'. In this
instance, the node Nb is held at the gate high voltage VGH, and
thus the transistor T5 is turned off
[0086] In the period {circle around (1)}, the node QB is
deactivated by the gate high voltage VGH applied through the
transistor T6. The transistor Td is turned off in response to the
deactivated node QB.
[0087] As a result, in the period {circle around (1)}, the emission
signal EM(1) of the gate low voltage VGL is output to the node Na
via the transistor Tu.
[0088] Referring to FIGS. 8 and 9B, in a period {circle around
(2)}, the external start signal EVST and the first clock signal
ECLK1 are input at the gate high voltage VGH, and the second clock
signal ECLK2 is input at the gate low voltage VGL.
[0089] In the period {circle around (2)}, the transistor T2 is
turned off in response to the external start signal EVST of the
gate high voltage VGH, and the transistor T5 is turned off in
response to the first clock signal ECLK1 of the gate high voltage
VGH. Further, the transistors T1 and T3 are turned on in response
to the second clock signal ECLK2 of the gate low voltage VGL.
[0090] In the period {circle around (2)}, the node Q is deactivated
to the gate high voltage VGH by the external start signal EVST
applied through the transistor T1. The transistors T6 and Tu are
turned off in response to the deactivated node Q.
[0091] In the period {circle around (2)}, the node Q' is activated
by the gate low voltage VGL applied through the transistor T3. The
transistor T4 is turned on in response to the activated node Q'.
The voltage of the node Nb is the gate high voltage VGH by the
first clock signal ECLK1 applied through the transistor T4. The
transistor T5 is turned off by the node Nb of the gate high voltage
VGH.
[0092] In the period {circle around (2)}, the node QB is floated by
the turn-off of the transistor T6. However, the voltage of the node
QB is held at the gate high voltage VGH of the period {circle
around (1)} due to the capacitor CQB. The transistor Td is turned
off in response to the node QB of the gate high voltage VGH.
[0093] In the period {circle around (2)}, the node Na is floated by
the turn-off of the transistors Tu and Td. However, the voltage of
the node Na is held at the gate low voltage VGL of the period
{circle around (1)} due to the capacitor CQ. In other words, in the
period {circle around (2)}, the emission signal EM(1) is held at
the gate low voltage VGL.
[0094] Referring to FIGS. 8 and 9C, in a period {circle around
(3)}, the external start signal EVST and the second clock signal
ECLK2 are input at the gate high voltage VGH, and the first clock
signal ECLK1 is input at the gate low voltage VGL.
[0095] In the period {circle around (3)}, the transistor T2 is
turned off in response to the external start signal EVST of the
gate high voltage VGH, and the transistor T5 is turned on in
response to the first clock signal ECLK1 of the gate low voltage
VGL. Further, the transistors T1 and T3 are turned off in response
to the second clock signal ECLK2 of the gate high voltage VGH.
[0096] In the period {circle around (3)}, the node Q is floated by
the turn-off of the transistor T1. Further, the node Q is held at
the gate high voltage VGH of the period {circle around (2)} and is
deactivated. The transistors T6 and Tu are turned off in response
to the deactivated node Q.
[0097] In the period {circle around (3)}, the voltage of the node
Nb is reduced to the gate low voltage VGL by the first clock signal
ECLK1 applied through the transistor T4. In this instance, because
the node Q' is floated and is coupled to the node Nb through the
capacitor CQ', the voltage of the node Q' is reduced by a reduction
in the voltage of the node Nb. In other words, the voltage of the
node Q' is bootstrapped from the gate low voltage VGL of the period
{circle around (2)} to a voltage VGL' less than the gate low
voltage VGL and maintains an activation state. The transistor T4 is
turned on in response to the node Q' of the activation state, and
the voltage of the node Nb is rapidly stabilized to the gate low
voltage VGL. The transistor T5 is stably turned on in response to
the node Nb of the gate low voltage VGL. When the transistor T5 is
stably turned on, change in the voltage of the node QB depending on
the first clock signal ECLK1 is stabilized.
[0098] In the period {circle around (3)}, the node QB is activated
to the gate low voltage VGL by the first clock signal ECLK1 applied
through the transistors T4 and T5. The transistor Td is turned on
in response to the activated node QB.
[0099] As a result, in the period {circle around (3)}, the emission
signal EM(1) of the gate high voltage VGH is output to the node Na
via the transistor Td. Namely, the emission signal EM(1) is
inverted to the gate high voltage VGH.
[0100] Referring to FIGS. 8 and 9D, in a period {circle around
(4)}, the external start signal EVST and the first clock signal
ECLK1 are input at the gate high voltage VGH, and the second clock
signal ECLK2 is input at the gate low voltage VGL.
[0101] In the period {circle around (4)}, the transistor T2 is
turned off in response to the external start signal EVST of the
gate high voltage VGH, and the transistor T5 is turned off in
response to the first clock signal ECLK1 of the gate high voltage
VGH. Further, the transistors T1 and T3 are turned on in response
to the second clock signal ECLK2 of the gate low voltage VGL.
[0102] In the period {circle around (4)}, the node Q is deactivated
to the gate high voltage VGH by the external start signal EVST
applied through the transistor T1. The transistors T6 and Tu are
turned off in response to the deactivated node Q.
[0103] In the period {circle around (4)}, the voltage of the node
Q' increases from the bootstrapping voltage VGL' to the gate low
voltage VGL due to the gate low voltage VGL applied through the
transistor T3. The transistor T4 maintains a turn-on state in
response to the node Q' of the gate low voltage VGL. The voltage of
the node Nb is the gate high voltage VGH by the first clock signal
ECLK1 applied through the transistor T4. The transistor T5 is
turned off by the node Nb of the gate high voltage VGH.
[0104] In the period {circle around (4)}, the node QB is floated by
the turn-off of the transistor T6. However, the voltage of the node
QB is held at the gate low voltage VGL of the period {circle around
(3)} due to the capacitor CQB. The transistor Td is turned on in
response to the node QB of the gate low voltage VGL.
[0105] As a result, in the period {circle around (4)}, the emission
signal EM(1) of the gate high voltage VGH is output to the node Na
via the transistor Td. Namely, the emission signal EM(1) is held at
the gate high voltage VGH.
[0106] The operation of the stage in the periods {circle around
(1)} to {circle around (4)} is summarized in Table 1 below.
TABLE-US-00001 TABLE 1 Period {circle around (1)} Period {circle
around (2)} Period {circle around (3)} Period {circle around (4)}
EVST EVST "VGL" .fwdarw. EVST "VGH" .fwdarw. EVST "VGH" .fwdarw.
EVST "VGH" .fwdarw. T2 "ON" T2 "OFF" T2 "OFF" T2 "OFF" ECLK1 ECLK1
"VGH" ECLK1 "VGH" .fwdarw. ECLK1 "VGL" .fwdarw. ECLK1 "VGH"
.fwdarw. T5 "OFF" T5 "ON" T5 "OFF" ECLK2 ECLK2 "VGH" .fwdarw. ECLK2
"VGL" .fwdarw. ECLK2 "VGH" .fwdarw. ECLK2 "VGL" .fwdarw. T1 and T3
"OFF" T1 and T3 "ON" T1 and T3 "OFF" T1 and T3 "ON" Q node Q node
"VGL" .fwdarw. Q node "VGH" .fwdarw. Q node "VGH" Q node "VGH"
.fwdarw. T6 and Tu "ON" T6 and Tu "OFF" hold .fwdarw. T6 and Tu
"OFF" T6 and Tu "OFF" Q' node Q' node "VGH" .fwdarw. Q' node "VGL"
.fwdarw. Q' node "VGL" Q' node "VGL" .fwdarw. T4 and T5 "OFF" T4
"ON" (bootstrapping) .fwdarw. T4 "ON" T4 "ON" QB node QB node "VGH"
.fwdarw. QB node "VGH" QB node "VGL" .fwdarw. QB node "VGL" Td
"OFF" hold .fwdarw. Td "OFF" Td "ON" hold .fwdarw. Td "ON" EM
Output EM(1) "VGL" EM(1) "VGL" EM(1) "VGH" EM(1) "VGH" hold
hold
[0107] Subsequently, referring to FIGS. 8 and 9E, in a period
{circle around (5)}, the external start signal EVST and the first
clock signal ECLK1 are input at the gate low voltage VGL, and the
second clock signal ECLK2 is input at the gate high voltage
VGH.
[0108] In the period {circle around (5)}, the transistor T2 is
turned on in response to the external start signal EVST of the gate
low voltage VGL, and the transistors T1 and T3 are turned off in
response to the second clock signal ECLK2 of the gate high voltage
VGH.
[0109] In the period {circle around (5)}, the node Q is floated by
the turn-off of the transistor T1. Further, the node Q is held at
the gate high voltage VGH of the period {circle around (4)} and is
deactivated. The transistors T6 and Tu are turned off in response
to the deactivated node Q.
[0110] In the period {circle around (5)}, the node Q' is
deactivated to the gate high voltage VGH by the second clock signal
ECLK2 applied through the transistor T2. The transistor T4 is
turned off in response to the deactivated node Q'. Further, the
voltage of the node Nb is held at the gate high voltage VGH of the
period {circle around (4)} due to the turn-off of the transistor
T4. The transistor T5 is turned off in response to the node Nb of
the gate high voltage VGH.
[0111] In the period {circle around (5)}, the node QB is floated by
the turn-off of the transistor T6. However, the voltage of the node
QB is held at the gate low voltage VGL of the period {circle around
(4)} due to the capacitor CQB. The transistor Td is turned on in
response to the node QB of the gate low voltage VGL.
[0112] As a result, in the period {circle around (5)}, the emission
signal EM(1) of the gate high voltage VGH is output to the node Na
via the transistor Td. Namely, the emission signal EM(1) is held at
the gate high voltage VGH.
[0113] Referring to FIGS. 8 and 9F, in a period {circle around
(6)}, the external start signal EVST and the second clock signal
ECLK2 are input at the gate low voltage VGL, and the first clock
signal ECLK1 is input at the gate high voltage VGH.
[0114] In the period {circle around (6)}, the transistor T2 is
turned on in response to the external start signal EVST of the gate
low voltage VGL, and the transistor T5 is turned off in response to
the first clock signal ECLK1 of the gate high voltage VGH. Further,
the transistors T1 and T3 are turned on in response to the second
clock signal ECLK2 of the gate low voltage VGL.
[0115] In the period {circle around (6)}, the node Q is activated
to the gate low voltage VGL by the external start signal EVST
applied through the transistor T1. The transistors T6 and Tu are
turned on in response to the activated node Q.
[0116] In the period {circle around (6)}, the node Q' is activated
to the gate low voltage VGL by the second clock signal ECLK2
applied through the transistor T2 and the gate low voltage VGL
applied through the transistor T3. The transistor T4 is turned on
in response to the activated node Q'. The voltage of the node Nb is
the gate high voltage VGH by the first clock signal ECLK1 applied
through the transistor T4. The transistor T5 is turned off by the
node Nb of the gate high voltage VGH.
[0117] In the period {circle around (6)}, the node QB is
deactivated by the gate high voltage VGH applied through the
transistor T6. The transistor Td is turned off in response to the
deactivated node QB.
[0118] As a result, in the period {circle around (6)}, the emission
signal EM(1) of the gate low voltage VGL is output to the node Na
via the transistor Tu. Namely, the emission signal EM(1) is
inverted to the gate low voltage VGL.
[0119] Referring to FIGS. 8 and 9G, in a period {circle around
(7)}, the external start signal EVST and the first clock signal
ECLK1 are input at the gate low voltage VGL, and the second clock
signal ECLK2 is input at the gate high voltage VGH.
[0120] In the period {circle around (7)}, the transistor T2 is
turned on in response to the external start signal EVST of the gate
low voltage VGL, and the transistors T1 and T3 are turned off in
response to the second clock signal ECLK2 of the gate high voltage
VGH.
[0121] In the period {circle around (7)}, the node Q is floated by
the turn-off of the transistor T1. Further, the node Q is held at
the gate low voltage VGL of the period {circle around (6)} and is
activated. The transistors T6 and Tu are turned on in response to
the activated node Q.
[0122] In the period {circle around (7)}, the node Q' is
deactivated to the gate high voltage VGH by the second clock signal
ECLK2 applied through the transistor T2. The transistor T4 is
turned off in response to the deactivated node Q'. Further, the
voltage of the node Nb is held at the gate high voltage VGH of the
period {circle around (6)} due to the turn-off of the transistor
T4. The transistor T5 is turned off in response to the node Nb of
the gate high voltage VGH.
[0123] In the period {circle around (7)}, the node QB is
deactivated by the gate high voltage VGH applied through the
transistor T6. The transistor Td is turned off in response to the
deactivated node QB.
[0124] As a result, in the period {circle around (7)}, the emission
signal EM(1) of the gate low voltage VGL is output to the node Na
via the transistor Tu. Namely, the emission signal EM(1) is held at
the gate low voltage VGL of the period {circle around (6)}.
[0125] The operation of the stage in the periods {circle around
(5)} to {circle around (7)} is summarized in Table 2 below.
TABLE-US-00002 TABLE 2 Period {circle around (5)} Period {circle
around (6)} Period {circle around (7)} EVST EVST "VGL" .fwdarw.
EVST "VGL" .fwdarw. EVST "VGL" .fwdarw. T2 "ON" T2 "ON" T2 "ON"
ECLK1 ECLK1 "VGL" ECLK1 "VGH" .fwdarw. ECLK1 "VGL" .fwdarw. T5
"OFF" T5 "ON" ECLK2 ECLK2 "VGH" .fwdarw. ECLK2 "VGL" .fwdarw. ECLK2
"VGH" .fwdarw. T1 and T3 "OFF" T1 and T3 "ON" T1 and T3 "OFF" Q
node Q node "VGH" Q node "VGL" .fwdarw. Q node "VGL" hold .fwdarw.
T6 and Tu "OFF" T6 and Tu "ON" hold .fwdarw. T6 and Tu "ON" Q' node
Q' node "VGH" .fwdarw. Q' node "VGL" .fwdarw. Q' node "VGH"
.fwdarw. T4 and T5 "OFF" T4 "ON" T4 "OFF" QB node QB node "VGL" QB
node "VGH" .fwdarw. QB node "VGH" hold .fwdarw. Td "ON" Td "OFF"
hold .fwdarw. Td "OFF" EM Output EM(1) "VGH" hold EM(1) "VGL" EM(1)
"VGL" hold
[0126] As shown in FIG. 8, the stage repeatedly performs the
operation of the period {circle around (6)} and the operation of
the period {circle around (7)} for a remaining time excluding the
periods {circle around (1)} to {circle around (7)} from one frame
period.
[0127] As described above, the embodiments of the disclosure can
greatly increase the reliability of the display device by securing
the operation stability of the emission driver.
[0128] Although the embodiments have been described with reference
to a number of illustrative embodiments thereof, numerous other
modifications and embodiments can be devised by those skilled in
the art that will fall within the scope of the principles of this
disclosure. In particular, various variations and modifications are
possible in the component parts and/or arrangements of the subject
combination arrangement within the scope of the disclosure, the
drawings and the appended claims. In addition to variations and
modifications in the component parts and/or arrangements,
alternative uses will also be apparent to those skilled in the
art.
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